Strontium Doping Effect on High-Temperature Oxidation of Nano-Ni Dispersed Alumina Composites

Abstract

Two sets of 0.1 mol% Sr-doped 5 vol% Ni/Al₂O₃ and undoped 5 vol% Ni/Al₂O₃ samples were fabricated by the pulsed electric current sintering technique to investigate the influence of Sr-doping effects on the high-temperature oxidation. Oxidation tests were conducted in air at temperature ranges of 1200–1400°C for 1–10 d. Oxidation of Ni within the matrix at high temperatures induced formations of the top surface layer and the oxidized zone. The top surface layer was composed of the oxidation product-NiAl₂O₄, while the oxidized zone consisted of Al₂O₃ matrix and NiAl₂O₄. Formation of the oxidized zone of undoped and Sr-doped samples followed the parabolic law. The parabolic rate constant of Sr-doped samples was approximately two times smaller than that of undoped samples. The apparent activation energies on the growth of the oxidized zone were determined to be 479 and 476 kJ/mol for undoped and Sr-doped 5Ni/Al₂O₃, respectively. Sr-doping reduced oxygen transport along Al₂O₃ grain boundaries and enhanced the high-temperature oxidation resistance of Ni/Al₂O₃.